The Celtics and Lakers are the flagship franchises of the NBA. They share a pedigree and a rivalry that is unmatched in the annals of the league. That’s all they have in common right now.

The teams were polar opposites on the parquet Thursday night at TD Garden in a game that was one in name only and wholly unworthy of this rivalry. The Celtics, who administered the basketball version of blunt trauma to the Lakers with a 116-95 beatdown, are rising to the occasion without point guard Rajon Rondo. They’re now winners of six straight. Proud. Strong. Defiant.

The Lakers are a Hollywood disaster movie, beset by injuries, infighting, and instability. Lethargic. Fragile. Diffident.

They came in as winners of three straight and six of seven. That felt like it happened 100 years ago. The Lakers got Dwight Howard back, but they’re not going anywhere.

In a season full of them, this was a new low for Kobe Bryant and Co. They suffered their largest defeat of the season. The Celtics put six players in double figures, led by Inglewood’s own Paul Pierce, who totaled 24 points, 7 rebounds, and 6 assists, despite sitting out the fourth quarter.

The Celtics left the Lakers in their wake with a 37-point third quarter in which they shot 76.2 percent from the field, making 16 of 21 shots.

It was the highest field goal percentage the Lakers had allowed in a quarter this season, topping the 73.9 percent the Knicks shot on Dec. 13. The 37 points tied the Celtics’ most productive quarter of the season, matching the second quarter against Sacramento Jan. 30.

“We can play a lot better than we played tonight. It’s one game. You flush it down the toilet and go on,” said Lakers coach Mike D’Antoni. “Tonight, we didn’t show anything. We didn’t do anything, and it wasn’t good from the get-go. We’ve got to find the juices and get back out there and do it. We won, what? Six out of [seven]? We do that every time we’ll make the playoffs. Now, we’ve got to start another streak.”

Cue, Jim Mora: “Playoffs? Playoffs?”

The Big Three of Pierce, Kevin Garnett, and Ray Allen made the idea of a union of veteran superstars look so easy in 2007-08. They had instant chemistry and instant identity and became instant champions. Watching the Lakers with Howard and Steve Nash stumble and backbite has only increased the admiration for what Doc Rivers and the Big Three were able to accomplish in their first season together.

The Ubuntu Boys had instant chemistry and identity. They had their issues, but winning wasn’t one of them. They won 66 games and raised Banner No. 17 by defeating the Lakers in the NBA Finals.

The idea of assembling a team of hoops Hessians looks good on paper, but on the court and in the locker room it’s rife with clashes of ego and contradictions of playing style. The Lakers are a cautionary tale for carelessly throwing stars together and thinking the sum of their stats adds up to winning basketball.

Nash celebrated his 39th birthday on Thursday, and he looked every bit of his 39 years during the game. The cagey Canadian was a non-factor.

Howard — after being publicly called out by Bryant and acting coy before the game, saying, “Game-time decision” — returned to the Lakers’ lineup after missing the last three games after aggravating the torn labrum in his right shoulder.

It felt like Bryant had goaded him into playing against his will.

Howard scored the Lakers’ first basket on a jump hook. He finished with 9 points and nine rebounds and was on the court in garbage time in the fourth quarter.

He ended his own suffering by fouling out with 5:07 left.

Even with Howard back, the Celtics outscored the Lakers, 58-36, in the paint.

Bryant was the Lakers’ life preserver — the only thing keeping them afloat. Kobe had 14 in the first half and 13 of the Lakers’ 25 points in the third quarter.

He hit shots over Courtney Lee that defied the laws of physics, and finished with 27 points.

It wasn’t enough. The Celtics led, 95-69, after three quarters. More and more the Lakers look like a sinking ship.

D’Antoni spared Bryant the indignity of being on the floor for any part of the fourth quarter of this blowout.

Bryant’s basketball biological clock is ticking, and playing on this ill-conceived, ill-fitting team is going to turn Kobe into a ticking time bomb at some point.

It was not Thursday night, though.

We got Mellow Mamba after the game. Perhaps, Bryant knows he’s already wasting his time with this team, so he shouldn’t waste his energy railing about a season that has gone off the rails.

“The roof just kind of caved in on us,” said Bryant. “We gave them a lot of transition baskets and easy points. They were hot. I can’t really remember them missing a shot. They played very well.”

On a night when Garnett (15 points, five rebounds) scored the 25,000th point of his storied career and a Celtics team made in his image displayed its fortitude and resourcefulness once again, Bryant, a generational peer of KG, seemed envious of the traits the Celtics have that his team is so sorely lacking.

“It’s typical Celtics basketball,” said Bryant. “They all just put their hard hats on and they go out and they figure things out.

“It just seems that when their backs are against the wall, that’s when you really see the best from them.”

You can’t say the same for the Lakers. They cower in the corner.

The Celtics aren’t going to give up this season. It appears that Howard and some other Lakers already have.